I use an 80 mm fan, but the actual amount of air pushed isn't all that much. The box I have mine in isn't sealed, and the air has to make two 90 degree turns to even get into the hose. It keeps the tower cool, but there isn't a hurricane going on in it.

If you have the room, why not use a scythe 120mm fan? Its something stupid like 9dB and pushes 33CFM worth of air. More isnt a bad thing in this case, as long as the fan does it quietly. Last thing you are going to want is a freakin tornado fan in there making all sorts of racket. I used these fans in my computers... damn near inaudible.

I am going to do this some time.. have more of those damn 80mm fans lying around than i know what to do with. I am currently making my stir plate.

Where does your hose attach to? Does it just sit in the tower?

The hose is a piece of stiff bilge tubing, and it's just pushed up the tower. It just stays in place with nothing to hold it there. It's held to the project box on the inside with thick electrical tape wrapped around it making a collar larger than the diameter of the hole it's passing through. The inside of the box looks a little ghetto, but it works.

Oh, also - the fan is a 12V fan using a wall adaptor. The adaptor I have is adjustable for voltage, and you can turn down the fan speed by turning down the voltage supplied to the fan.

I was actually trying to think of a way to connect the fridge light to a fan. After you take the shelves out, the light stays on all the time. Thats a great source for power built right into the fridge. The only thing I could come up with is either soldering leads directly on to the light bulb socket, or breaking a light bulb and soldering leads on to the light posts. Neither are the most secure, but its the best I could think of with limited thought and limited looking into screw in plug adapters